dt-bindings: gpu: mali-utgard: Add Rockchip Utgard Malis

Some (older or lower power) Rockchip socs use Utgard-based Mali-GPUs.
So add the necessary compatibles for them. As the setup is the same for
all of them (needing only the additional reset line), they get added in
a somewhat condensed form, to not inflate the document unnecessary.
Signed-off-by: NHeiko Stuebner <heiko@sntech.de>
Acked-by: NRob Herring <robh@kernel.org>

Documentation/devicetree/bindings/gpu/arm,mali-utgard.txt

@@ -13,6 +13,10 @@ Required properties:
       + allwinner,sun50i-h5-mali
       + amlogic,meson-gxbb-mali
       + amlogic,meson-gxl-mali
+      + rockchip,rk3036-mali
+      + rockchip,rk3066-mali
+      + rockchip,rk3188-mali
+      + rockchip,rk3228-mali
       + stericsson,db8500-mali
 
   - reg: Physical base address and length of the GPU registers
@@ -63,6 +67,10 @@ to specify one more vendor-specific compatible, among:
     Required properties:
       * resets: phandle to the reset line for the GPU
 
+  - Rockchip variants:
+    Required properties:
+      * resets: phandle to the reset line for the GPU
+
   - stericsson,db8500-mali
     Required properties:
       * interrupt-names and interrupts: